Sunday, February 12, 2017

Saguaro Saturday!

My buddy Donna was down over the weekend. Since our Jeep outing last Fall, a group of fellow astronomy nuts has been debating where to go on a 4WD outing as the weather gets warmer, and someone suggested a petroglyph site in Saguaro National Park, western unit. It isn't a difficult drive even for a passenger vehicle, so Donna and I hit the road on a lovely Saturday yesterday to check it out. I haven't been there in a good 15 years, so reviewed the maps and hit the road for a couple-hour road trip.

The first stop was Gates Pass, where Speedway/Anklam Road crosses the Tucson Mountain Range. It is spectacularly scenic with groves of saguaro cacti, and as shown at left, the view opening up towards the west quite dramatically. The main photo was taken with a 16mm full-frame fisheye on the Canon 6D, so has a 180 degree diagonal field-of-view. To show some of the details at reasonable scale, the inset shows a blow-up of Kitt Peak National Observatory about 35 miles to the SW with a 500mm lens and blended with the magic of Photoshop...

The view towards the north is no less exciting, even in the dull light of midday - saguaros all the way up the slopes to the profile of the mountain ridge, though the fisheye lens doesn't show them much. It again takes the inset from the 500mm lens to bring out those details...

We drove down past the West Unit's visitor center and checked in (free, thanks to my Golden-Ager NPS pass). We continued north a bit on Sandario Road before hitting Golden Gate Road, a dirt road we followed for a couple miles to the Signal Hill picnic area. From there we could spot the petroglyph site about a 1km hike away, with the trail spiraling up the far north side. An image is shown at left, with a group atop the hill, behind a protective fence checking out petroglyphs. It didn't take us long to hike over a well-maintained trail - literally a freeway compared to some of the raw trails I've seen in the SW!

The petroglyphs were made by the Hohokam culture about 1,000 years ago and are quite striking. The main spiral is shown at left, with many others scattered about the stones of the hilltop. Besides the spirals and possible symbols for the sun and moon, you can also imagine figures of deer or sheep, scorpions and snakes. Niles Root has done some spectacular images and analysis, proving that the site was used as an astronomical calendar, finding dates of the summer solstice(first day of Summer) and vernal and autumnal equinoxes (start of Spring and Fall). His website with fascinating photos and descriptions is linked here.

A wider shot of the area showing a few more symbols is shown at left. The main spiral shown above is now near the left edge, with more visible at lower right. And at right is another large spiral on a nearly horizontal stone. Root's description didn't mention the symbols over here on the west side, so there are still mysteries about!

With all the examinations of the
petroglyphs, you forget you are still in Saguaro National Park, and the view towards the NE towards Mount Lemmon, shown at left shows the forest of Saguaros in the area. That is Mount Lemmon at far distance at center.

And because THIS IS MY BLOG, I've got lots of 3D photos too! So grab your red/blue glasses and follow along. Since I just showed the cactus forest at left, at right is an anaglyph (3D shot by adding another shot taken a couple feet away). Using the glasses, each of your eyes sees the appropriate frame and your brain reconstructs a stereo image.

And, of course, I've got 3Ds of the
petroglyphs too!  At left is a close-up of the main spiral at the site.  This was taken with a telephoto and is a "hyperstereo", taken with a baseline further apart than your normal eye separation.  Doing it this way emphasizes the stereo effect, amplifying the unevenness of the stone and spiral itself! 

At right is a wider field including some of the mountainous background too. and finally below, is the wide shot showing other petroglyphs...

We returned to Sandario Road, but rather than return the way we came, continued north and returned to Tucson on Picture Rocks Road  (so named because of the numerous petroglyphs), making a big loop for our Saturday adventure. 

No comments: